chemical physics of discharges - Argonne National Laboratory

5'
.
'
I 1
257
co, with excess H2, and N admitted either downstream of T(1), as indicated in
2
Fig. 1, or in the manifold system. The latter experiment was believed to be a purer
The liquid nitrogen.
Source Of CO and was employed for most of the preparations.
temperature of T( 1) and its packing trapped all significant water produced in the
water-gas reaction, as well as remaining COz. It became apparent that if T(l) does
not trap all the significant water, that no polymer forms at T(2), due either to a reaction
of H20 or discharge products therefrom (3) with polymer precursors, or to
the interference of water to the deposition of the polymer as a film on the cold inner
tube of T(2). I
The polymers at low N flows are characterized by being transparent, yellow,
tightly adherent films. At fiigher N2 flows, the transparency decreases, and film
strength appears to decrease, indicating perhaps lower molecular weight materials
being formed.
The production of the polymer under the flow conditions listed in Tabie I appears
critically dependent on the system pressure. In the experiments, the flow8 bf CO or
CO and H were maintained at nearly constant values while the nitrogen flow rate
waH varied The very low flow rates of N resulted from permeation through a very
short segment of Tygon tubing initially connecting
2
R(l) to the manifold outlet. These
rates of permeation were measured by observing rates of system pressure increases
with time, and checked by He permeation with the mass spectrometer at the same
point. In Run 861, the uncertainty is probably an order of magnitude; in Runs 631
and 291, the uncertainties are half that. In any case, the low flows of N2 in the initial
experiments were much less than measured flow rates in subsequent experiments,
which indicate (Table I) that less and less polymer is produced other ases fixed) as
ca. 107 cm' min-', no polymer
was o%served to form at all.
1 the N flow rate increases. At a very high N2 flow, -
1
).
TABLE 1. Flow Conditions for Several Sample Preparations
I
Run
I Flow Rates , cm3 min-l
Power, Watts Run
~
h '
b
co2 co
N2 H2
861 1. 18 --- 1-3. 1~10-~ 3. 65
63 1 1.43 --- 3. 9x10-3 3. 95
I 291 ---- 2. 18 -42. 5x10-' 4.43
bl 931 1.25 --- 1. 26 3. 60
6 890 1.36 --- 107 3. 74
i
I 991 1.36 --- 9. 88 3. 83
psYs, Time;
torr R(1) R(2) Mins.
.310 330 1, 355 680
.320 --- 280 414
.36 300 --- 720
.45 320 350 463
.75 320 410 460
2.47 320 360 273
1 Table I1 indicates elemental analyses for C, H, N, and 0 for several runs. The per
cent nitrogen is found to increase as the flow of N increases. This suggests, up to
a certain point, that one can produce in this experiment 2 tailored polymers containing
a controllable amount of a given constituent by controlling its flow rate. The dependence
of per cent nitrogen found in the polymer on flow rate is given in Figure 2.
Why no polymer forms at high system pressures, ca. 1.0 mm Hg pressure, is
perhaps due to competing gas phase processes (4). ThFsame types of polymers no
doubt may be arrived at by substitution of ammonia for the N - H2 mixture, since
one often achieves many similar results irrespective of whetker one uses N
or NH3. Little molecular or atomic oxygen, as such, should be produced in 2 these +H2
.